There are speaker apparatuses that output a sound (voice) having a predetermined frequency band. For example, one of the speaker apparatuses oscillates an oscillating body (sound diaphragm) by expansion and contraction of an oscillating element such as a piezoelectric element and a magnetostrictor, and outputs a sound (for example, see Patent Literature 1).
In the speaker apparatus described in Patent Literature 1, a driving signal is input to an oscillating element that functions as a driving part, the oscillating element is expanded and contracted, an oscillating body is oscillated by expansion and contraction of the oscillating element, and a sound is output.
In the speaker apparatus where the oscillating element is used as the driving part that oscillates the oscillating body, it is possible to obtain a great driving force and to ensure a good sound output state.